The effect of pre-operative aspirin on bleeding, transfusion, myocardial infarction, and mortality in coronary artery bypass surgery: a systematic review of randomized and observational studies.

AIMS: To obtain estimates of the efficacy and safety of pre-operative aspirin in patients undergoing coronary artery bypass grafting (CABG). METHODS AND RESULTS: Eligible studies included randomized controlled trials (RCTs) and observational studies of patients undergoing CABG, comparing pre-operative aspirin with no aspirin/placebo, and reporting at least one of our primary outcomes. In eight RCTs (n = 805), pre-operative aspirin increased post-operative bleeding [Mean difference (MD), 104.9 mL; 95% confidence interval (CI), 19.2-190.6; P = 0.016] and reoperation [odds ratio (OR), 2.52; 95% CI, 1.18-5.38; P = 0.017), but not transfusion requirements (MD, 0.62 units; 95% CI, -0.06-1.30; P = 0.072). Subgroup analysis suggested that bleeding was increased with aspirin doses > or =325 mg/day, but not with lower doses. In 14 observational studies (n = 4485), pre-operative aspirin increased post-operative bleeding (MD, 113.6 mL; 95% CI, 45.2-182.0; P = 0.001) and transfusion requirements (MD, 0.34; 95% CI, 0.12-0.56 units; P = 0.002), but not reoperation (OR, 1.12; 95% CI, 0.69-1.83; P = 0.647). Neither analysis detected a significant effect on myocardial infarction or death. CONCLUSION: Pre-operative aspirin increases post-operative bleeding, but this may be avoided by the use of aspirin doses <325 mg/day. Most of the RCTs are old and the meta-analysis was underpowered for efficacy outcomes. A large randomized trial is necessary to determine the safety and efficacy of pre-operative aspirin in the setting of contemporary cardiac surgical practice.